1. Field of the Invention
The present invention relates to a cooking oven capable of rotating a turntable with a cooking object placed thereon, of moving the turntable into and out of a heating chamber, of determining the time required for the object to be heated in agreement with its weight, and of controlling the way of moving the turntable.
2. Description of the Related Art
As shown in FIG. 1, a conventional cooking oven (Japanese Patent Laid-Open No. 161214/1990) includes a heating chamber 1 for accommodating an object to be heated, a door 2 which can be opened and shut, the door being fitted to the front of the cooking oven, and a moving means 18 provided with a motor 19 for rotating a turntable 3 on the base of the heating chamber 1 and a moving unit 20. Consequently, the turntable 3 can be loaded on the top surface of the moving means 18 before being moved, together with the moving means 18, by the moving unit 20 into and out of the heating chamber 1.
When cooking, food is placed on the turntable 3 and the door 2 is shut. Then the food is cooked by means of a microwave or electrical heating. It has also been arranged that the turntable 3 can be rotated by the motor 19 during the cooking operation and can be moved by the moving unit 20 into and out of the heating chamber 1. In this way, an object to be heated is readily placed into and out of the heating chamber 1.
However, the conventional cooking oven, as described above, is what has incorporated the turntable 3, the motor 19 and the moving unit 20 into the moving means 18. As a result, lead wires for use in supplying power to the motor 19 and the moving unit 20 have been so arranged that they are long enough to be proportional to the movement of the turntable 3 or otherwise that there is employed a special reinforced lead wire capable of withstanding the stress resulting from the movement.
When a microwave energy is used as heating means, the motor 19 of the turntable 3, the moving unit 20 and the like are irradiated with a microwave and the microwave irradiation may cause a spark, abnormal heating and the like, thus interfering with the cooking operation. When the microwave is propagated outside the heating chamber 1 with the lead wire as an antenna, a control unit may be heat-damaged thereby or caused to malfunction because of high-frequency noise. The disadvantage is that the microwave is not usable as such a heating means, that is, the dangers enumerated above limit such heating means for use to electric heaters.
Moreover, the moving means 18 incorporating the turntable 3 together with the motor 19 for rotating the turntable 3 and the moving unit 20 may be hindered from smoothly moving back and forth because of smoke black resulting from cooking and sticking to the moving means 18, because of waste food and of liquid infiltration. When any one of the essential mechanical parts is soiled, it is infeasible to take away such a part for washing and this tends to lower not only its cleanliness but also its sanitary conditions. The system as a whole is disadvantageous in that it is apt to become thus large-scaled and costly and besides a large exposed hot portion is tantamount to suffering from a possible burn.
Japanese Utility Model Unexamined Publication No. Hei 4-57108 proposes a cooking oven designed to facilitate placing and replacing a cooking object in a heating chamber by interlocking the movement of a turntable with that of its door in addition to rotating the turntable by means of a drive unit.
However, the cooking oven proposed above is disadvantageous for automatic cooking as the load of the object placed on the turntable is supported with the bottom of the heating chamber and cannot be weighed. Since the movement of the turntable is interlocked with that of the door, moreover, the speed at moving the turntable into and out of the heating chamber is affected by the speed at which the door is opened and shut; consequently, the former tends to vary. The variation of the speed may cause unstable bowls such as bottles and cups to topple down or may cause a cooking object to fall over by the shock produced at the time the door is opened or shut or may cause what is liquid to spill. In other words, there is the risk of burning oneself when such an object is hot.
Moreover, the object is taken out each time the door is opened and this may lower its temperature even when it is only needed to check the cooking result without taking it out. The problem is that the freedom of taking the object in and out is lacking.
Since the turntable is coupled to a member for coupling the door, the rear side of the turntable with a receiving tray remains inside the heating chamber even when the door is opened. When a liquid substance is accidentally spilt, it has been very difficult to clean not only the turntable with the receiving tray but also its rear side as well as the bottom surface of the heating chamber. Moreover, the moving distance of the turntable is determined by the length of the coupling member, which has to be made longer as a portion to be taken out increases. In this case, the coupling member may become an obstacle while the object is taken in and out. The joint between the coupling member and the coupling part of the turntable corresponds to a shaft for use in opening and shutting the door and makes an arcuate locus while the door is opened and shut. In other words, the turntable is caused to move back and forth while it is moved up and down. As a result, the coupling member cannot be made much longer to decrease the vertical movement of the turntable. The problem in this case is that the longitudinal movement of the turntable is restricted.
A cogwheel for rotating the turntable and the cogwheel of the drive unit are engaged with and released from each other each time the door is opened and shut. Therefore, these cogwheels are apt to wear rapidly and when the door is quickly shut, they are forced to strike against each other; consequently, there arise various problems therefrom including the damage of the cogwheels, the deformation of the shaft and so forth.